if（c>b)报错

# include <reg52.h>
# define uint unsigned
# define uchar unsigned char

sbit c = P0^0;
sbit d = P0^1;
sbit led = P0^2;
uchar code table1[] = {0x01, 0x02, 0x04, 0x08};
uchar code table2[] = {0x08, 0x04, 0x02, 0x01};

void delay(uint x)
{
    uchar i;
    while(x --)
    {
        for(i = 80; i > 0; i --);
    }
}

void main()
{
    EA = 1;
    while(1)
    {
        if(c == d)
        {   
            led = 0;
            delay(10);
        }
        else
        {
            if (c > d)
                 EX0 = 1;
            else
                EX1 = 1;
        }
    }            
}

void int0() interrupt 0
{
    uchar a;
    for(a = 0; a < 4; a ++)
    {
        P3 = table1[a];
        delay(10);
    }
}

void int1() interrupt 2
{
    uchar b;
    for(b = 0; b < 4; b ++)
    {
        P3 = table2[b];
        delay(10);
    }
}
这里：if(c>b)这一行提示'>' bad operand type.怎么回事啊？
谢谢~